P03.13.B CORTICAL DWI-GD MISMATCH SIGN AS A SPECIFIC IMAGING BIOMARKER OF PRIMARY CNS LYMPHOMA

Abstract BACKGROUND Previous studies have focused on differentiating glioblastoma, IDH-wildtype (GB), from primary CNS lymphoma (PCNSL) based on the peritumoral area and white matter invasion. In this study, we will focus on the peritumoral area of the PCNSL and GB superficial lesions. MATERIAL AND METHODS We retrospectively reviewed the preoperative images of patients with pathologically confirmed GB and PCNSL. We focused on the differences in anatomical lesions between Gd-T1WI and diffusion-weighted images (DWI). The cortical DWI-Gd mismatch sign was defined as a DWI high-intensity lesion that appears covering both gray and white matter, with corresponding gadolinium-enhanced lesion limited to the subcortical white matter, delineating the gray-white matter junction. Non-contrast-enhanced and DWI iso-hypointensity lesions were not accounted for as positive cortical DWI-Gdmismatch signs. RESULTS A total 65 cases of histologically confirmed PCNSL and 67 cases of GB were identified from 2006 to 2023. Thirteen cases (20%) of PCNSL and 35 cases (52.2%) of GB presented with superficial lesion. Seven cases (53.8%) out of 13 cases of PCNSL with superficial lesions presented with the cortical DWI-Gd mismatch sign. This sign appears exclusively in PCNSL and was not observed in GB (Fisher’s exact test p= 0.001, sensitivity: 53.85%, specificity: 100%). This sign was primarily observed in females (n=6, 85.7%) with a mean age of 60.42 ± 15.2 years. Five cases were pathologically confirmed as DLBCL non-GCB type, and 2 cases were DLBCL, GCB type. CONCLUSION Cortical DWI-Gd mismatch sign could serve as a specific imaging diagnostic biomarker for PCNSL.